Originally Posted by llang269
That’s the plan, the Submersive up front in the corners and the 3 F18’s in the back corners and center
You probably already know all this, but I'll throw it out there for others reading along... because that's what we do in the Seaton threads... we HELP each other!
When Harman looked at the optimum number of subwoofers and their locations, they concluded that there was little if any benefit to using more than 4 "sources" of bass. They also found that the 4 "mid-wall" positions where optimal for smoothing of response and seat-to-seat consistency. 4 corner locations offered increased output, but less potential for smoothing and consistency over more seats. Their third suggestion was for two subs, one in front and one in back, which was almost as good as 4 subs mid-wall for smoothing and consistency, but offered less total output.
Of course, one of the requirements of their study was a sealed rectangular room, and their findings may not apply to any other room configuration. They also sent the exact same signal to all subwoofers, which meant they gain-matched the subs. If one intends to level-match their subs, using Audyssey, or some other RC system, Harman's findings may also not apply. Another requirement was for "identical" subwoofers. I know the F18's and the Submersives are very similar, but adding identical subs *might* be better.
Earl Geddes suggests a completely different system for subwoofer selection, placement and optimization: He suggests using a "odd" number of subs, with one sub being the "primary" and the other subs being "filler" subs. He also doesn't use gain-matching or level-matching. He bases his level settings on FR measurements. https://mehlau.net/audio/multisub_geddes/
Personally, I use a hybrid of the two techniques. I place my 3 Submersives somewhat randomly around my asymmetrical room, with 2 of them being equidistant to the LP so I can set one Distance setting for both. These two subs are well-separated so they provide differing modal responses. I gain-match all 3 of them, and set Distances and EQ with Audyssey. I worked closely with Mark to optimize my system. He heard it afterwards and said he had nothing else to offer to improve it.
Before you invest in the 3rd, 4th or, (especially), the 5th sub, I would encourage you talk to Mark about your setup and your calibration and EQ systems. He *may* suggest just 4, or he *may* suggest 8!
Or, he may suggest something in between. Either way, he's the resident expert on truly high performance subwoofer systems, and he can help you configure things for optimal response, as well as fiscal responsibility.
Edit: Mark's help in configuring my system and educating me about the ins 'n outs of subwoofer *system* optimization were completely FREE, and completely OVER-THE-TOP!